1. Field of the Invention
This invention relates to injecting a micellar dispersion into a subterranean formation and displacing it toward a production means in fluid communication with the formation to recover crude oil therethrough.
2. Description of the Prior Art
The prior art recognizes that micellar dispersions are useful to displace crude oil from subterranean formations, examples of U.S. Pat. Nos. include 3,254,714; 3,275,075; 3,506,070; 3,497,006, 3,613,786; 3,734,185; 3,740,343; 3,827,496; and other patents defining surfactant systems and assigned to Esso Production and Research, Shell Oil Company, Union Oil Company, etc. The micellar dispersion can be water-external or oil-external. The prior art generally teaches that the injected micellar dispersion is followed by an aqueous mobility buffer and this in turn followed by a water drive. In general, the above patents teach that the surfactant useful in the micellar dispersion is a petroleum sulfonate obtained from gas oils or other fractions of crude oil. Much of the prior art relating to sulfonation to produce petroleum sulfonates describes processes wherein the petroleum sulfonate produced is a by-product of the polishing of lubricating stock. Different processes are needed to produce the different types of petroleum sulfonates needed for widespread effective and economic oil recovery. Processes such as those in copending U.S. patent Ser. Nos. 513,692 and 376,657 teach processes wherein whole or topped crude oil are sulfonated to obtain sulfonates useful in crude oil recovery. The micellar dispersions using these new types of petroleum sulfonates contain cosurfactants. In the processes of our applications, whole or topped crude is sulfonated with sulfur trioxide and the sulfonic acids neutralized with a monovalent base to obtain the desired sulfonate, and unreacted hydrocarbon can be removed either before or after neutralization.